I'm Alex, with the Shopify team!
Hmm, I see - I'm sorry to hear it. I've been to have a look and you're quite right; those other images appear on a desktop browser, even in a very small window, but they don't appear on a mobile device - though, oddly, I've found that if you switch to landscape view on a mobile and then reload the page, they'll appear.
That being the case, it looks like this is likely an issue with how your theme handles responsiveness for mobile viewing, rather than an issue with your store itself or the images that you're using. Your best option here is to reach out to the developer of that theme for help in resolving this. If this is a theme created by Shopify, just reach out to us - we'll be more than happy to take a closer look into this for you!
If this is a third-party theme, made by a developer outside Shopify, then you can reach out to them directly - if you're not sure who developed that theme, you can find this information by going in your admin to online store > themes and clicking the customize button. In the next screen there will be a menu over to the left; click on the theme settings tab at the top of this menu and scroll down, you should see it there.
If the developer of this theme isn't able to help, I'd recommend reaching out to one of the third-party design experts for hire that we have listed - they'd be able to look into this and help resolve the issue for you!
Hope that's helped! Please feel free to let me know, and you can always give us a call or start a live chat at any time. We're open 24/7 for your convenience and always happy to assist!
Alex | Shopify
Welcome to the Shopify community!
Please share your site URL,
So I will check and provide a solution here.